The present invention relates to the field of wireless power transfer, and more particularly to systems and methods of transferring wireless power through conductive metals.
There has been a widespread increase in efforts to implement wireless power transfer systems in both commercial and residential settings. Wireless power systems offer the promise of eliminating power/charging cords for a wide range of electrically powered devices, including not only handheld electronics, such as cell phones, media players, wireless headsets and personal digital assistants, but also higher power devices, such as appliances, tools and electric vehicles. Inductive wireless power transfer systems use electromagnetic fields to transfer power from the power supply to the remote device without the need for wires or any direct electrical contact.
In many applications, the wireless power supply includes a power transfer surface on which a remote device can be placed to receive wireless power. The wireless power supply typically includes a primary coil, or other electromagnetic field transmitter, positioned below the power transfer surface. In use, the primary coil produces an electromagnetic field that is present over the power transfer surface. As a result, a remote device placed on the power transfer surface will be located within and capable of receiving power through the electromagnetic field.
One of the potential challenges faced by wireless power systems arises from the fact that electromagnetic fields interact with conductive materials. More specifically, when conductive materials are placed in the presence of a varying electromagnetic field, the field generates eddy currents within conductive material, which act to dissipate the electromagnetic field and produce heat. This principle is well known and conductive materials are commonly used when it is desirable to shield electromagnetic fields. Given the inherent nature of conductive materials, the use of conductive materials in an around wireless power supplies can be problematic. Because conductive materials are an integral part of many electric and electrical components, these problems can place significant limitations on the types of electric and electrical components that can be situated in and around wireless power supplies, particularly in the electromagnetic field path between the primary coil and the remote device.